The present invention relates in general to a communication system for transmitting voice information between front and rear seating areas in a vehicle, and more specifically, to a voice enhancement system avoiding audible feedback and which is easily integrated with an audio entertainment system and/or a mobile transceiver.
In a typical Passenger vehicle, a driver of the vehicle must, of necessity, face forward in the direction of forward travel of the vehicle. In passenger compartments containing additional rows of seats, the driver and any other front seat passengers are thus facing away from rear seat occupants. Consequently, in a car or van, for example, a backseat passenger may have difficulty understanding or hearing the speech of the driver or anyone else in the front row.
In order to improve intelligibility of speech, a front seat occupant may turn his or her head to face the rear seat occupants, or a rear passenger may lean forward to better hear the front seat occupant. However, these actions may cause inconvenience and discomfort for them.
It is known to use a microphone in the front or rear seating area to pick up voices which are then amplified and reproduced by an electromechanical transducer (e.g., speaker) in another seating area. A particular problem encountered in such a system is acoustic feedback between the speaker and microphone which can produce howling in the speaker when such feedback is excessive.
McGregor et al, U.S. Pat. No. 4,965,833, discloses a voice enhancer system wherein a frequency shifter increases the voice frequencies by about 5 Hz to prevent acoustical howl-around. In addition to microphones and speakers, McGregor et al employs a preamplifier, a lowpass filter, a highpass filter, a notch filter, a frequency shifter, and a power amplifier.
In systems intended for high volume production, it is highly desirable to reduce the part count and cost of a communication system. It is especially desirable to avoid the need for a frequency shifter which is a complicated and relatively expensive component.
Modern automobiles typically include an audio entertainment system (e.g., a radio) and often include a mobile transceiver (e.g., a cellular phone). In order to improve system operation and reduce cost, it is also desirable to integrate any passenger communication system with the audio entertainment system and/or the mobile transceiver.